This invention relates to an improved roller shutter assembly especially for a roller shutter intended for use as a garage door or for a similar structure.
Spring tensioned roller shutters or blinds are commonly known for many uses for example as cabinet shutters, door or window shutters etc. In such constructions it is usual for the assembly to comprise a generally cylindrical roller onto which the shutter or blind is wound, the roller being journalled at each end by carrying means which are fixed relative thereto. The roller is connected to the carrying means by way of a co-axial central core or similar arrangement and by a helical spring such that rotation of the roller in one direction will cause tensioning of the spring. When the tension is released rotation of the roller in the opposite direction is caused.
It will thus be appreciated that in this way a shutter attached to the roller may be unfurled causing tensioning of the attached spring which is then held in place by a ratchet or similar mechanism. When the ratchet is released the tension in the spring causes the roller to rotate thereby rewinding the shutter thereon and raising it from its closed position.
Such an assembly has several problems. In the first place, is not easy to maintain the assembly in working condition especially if there is a breakage of the helical spring which will require complete disassembly in order to rectify the breakage. Furthermore the helical spring must be pre-tensioned before use which can be especially difficult where the roller shutter is intended for use as a garage door and is consequently of a substantial weight. Furthermore the construction described is not easy to provide with a motor as the drive must be applied to the cylindrical roller and not to the carrying means are the more easily accessible.
Further disadvantages of the known configuration are especially apparent when the known construction used for a garage door comprising a plurality of metal or similar slats. The substantial size of a garage door means that the blind in question will invariably be fairly hearty and the slats of fairly broad width. This causes a problem insuring the smooth winding of the slats which because of their thickness will form an irregularly shaped roll. Furthermore there will always be a transition point between one layer of slats around the roller and the next causing a bump or protrusion the rolled shutter surface.